The research detailed in this application will concern itself principally with the mechanism of cellular immunity. A protein isolated from the sea star Asterias forbesi, sea star factor (SSF), simulates many of the effector substances released from immunized T cells exposed to specific antigen, and may be used as a probe for T cell function. While not toxic for lymphocytes in vitro, this protein inhibits the uptake of tritiated thymidine by mammalian lymphocytes in response to T cell mitogens or in mixed lymphocyte cultures. The lymphokin-like activities of this material (inhibition of macrophage migration, mononuclear chemotaxis, macrophage-activating effects, etc.) might be due either to a direct effect on mononuclear phagocytic cells or to stimulation of T cell-product synthesis. The application of this material to tumor immunity will be studied, using transplantable mouse methylcholanthrene-induced tumors in attempts to investigate possible adjuvant effects when minute amounts of SSF are coupled to tumor cells for specific immunization of syngeneic hosts. Bibliographic references: Effect of sea star factor (SSF) on transplanted syngeneic and allogeneic lympho-hematopoietic cells. D.L. Klein, G.W. Santos, and R.A. Prendergast, Fed. Proc. 34:1010, 1975. Marine invertebrate origin of a reactant to mammalian T cells. R.A. Prendergast, C.S. Henney, and G.A. Cole, Ann. N.Y. Acad. Sci. 234:7, 1974.